Earth's telescope is a telescope that belongs to Earth . Earth would usually look through it to find discoveries and to help the humans with their knowledge of the universe . Earth is willing to share her telescope with other celestial bodies as shown in All seeing future where she gives her telescope to Mars and Mercury.
Mercury would usually look through the telescope to possibly find some new and exciting discoveries but he is unlucky because to him , he doesn't find anything interesting .
The telescope apparently has the ability to turn planets flat as shown in Earth has truly changed shape . The telescope is only able to do this when thrown very quickly .
The telescope has the appearance of a pirates telescope instead of a scientific space telescope . Mars acknowledged this in the telescope's debut .
In All seeing future Mars is looking through a telescope when Earth asks Mars if he's discovered anything yet . Mars discovered that he's using a pirate telescope and not a space telescope and that he saw nothing but space . Mercury asks Earth if he can use his telescope and Earth says yes but Mars wishes him good luck . Mercury looks through the telescope and sees nothing interesting and thinks he could see something else interesting in the next Mercurian day .
In Earth has truly changed shape , Mercury was still looking through the telescope when he furiously threw it unknowlingly at Earth causing her to be flat for a period of time . After Earth was reverted back into a sphere Moon had an idea that Mercury made her flat . After that , Mercury was hit with the telescope causing him to be flat which caused a rivalry and a confused Haumea.